Triangle Calculator

Calculate triangle area, perimeter, and type using sides, base/height, or angles. Fast, accurate, and easy for all triangle problems.

Triangle Calculator: Domain Knowledge

A triangle is a three-sided polygon with three angles. The sum of the interior angles of any triangle is always 180°. Triangles are fundamental shapes in geometry and are classified based on their side lengths (equilateral, isosceles, scalene) and angles (acute, right, obtuse). Triangles are used in trigonometry, engineering, architecture, and many real-world applications. Understanding triangle properties is essential for solving problems in mathematics, physics, and design.

  • Equilateral Triangle: All sides and angles are equal (each angle is 60°).
  • Isosceles Triangle: Two sides and two angles are equal.
  • Scalene Triangle: All sides and angles are different.
  • Right Triangle: Has one 90° angle.
  • Heron's Formula: Area = √(s(s-a)(s-b)(s-c)), where s = (a+b+c)/2.
  • Base & Height: Area = (base × height) / 2.
  • Trigonometric Formula: Area = ½ab sin(C) for two sides and the included angle.

How This Tool Works

The Triangle Calculator allows you to compute the area, perimeter, and type of a triangle using various input methods: three sides, base and height, or two sides and the included angle. The tool uses Heron's formula for three sides, the standard base-height formula, and trigonometric calculations for two sides and an angle. It also determines the triangle type (equilateral, isosceles, scalene, right, or invalid) based on the side lengths. All calculations are performed instantly in your browser for privacy and speed.

Enter the known values, select the calculation type, and click Calculate. The tool will display the area, perimeter, and triangle type, along with helpful explanations. This makes it ideal for students, teachers, engineers, and anyone needing quick triangle solutions.

Key Features

  • Multiple Calculation Methods: Use three sides, base and height, or two sides and an angle.
  • Instant Results: Get area, perimeter, and triangle type immediately after entering values.
  • Responsive Design: Works perfectly on desktop (85% width) and mobile (95% width).
  • Educational: Shows triangle classification and formulas for learning purposes.
  • Privacy First: All calculations are done locally in your browser.
  • Accessible: Clean interface, keyboard navigation, and screen reader support.
  • Clear Error Handling: Alerts for invalid triangles or missing/incorrect input.

The Triangle Calculator is a reliable tool for students, professionals, and hobbyists. It is updated regularly for accuracy and usability.

Common Use Cases

  • Homework & Exams: Quickly solve triangle problems for school or college assignments.
  • Engineering & Construction: Calculate areas and perimeters for design and building projects.
  • Trigonometry Practice: Explore relationships between sides and angles for learning.
  • Art & Design: Determine triangle dimensions for creative projects.
  • Everyday Math: Use for DIY, crafts, or any scenario involving triangles.
  • Teaching Aid: Demonstrate triangle properties and formulas in the classroom.

The calculator adapts to a wide range of needs, making triangle math accessible to everyone.

Step-by-Step Guide

  1. Select Calculation Type: Choose whether you want to find area, angles, or sides.
  2. Enter Known Values: Fill in the side lengths, base/height, or angles as needed.
  3. Click Calculate: Press the Calculate button to see results instantly.
  4. Review Results: View area, perimeter, and triangle type in the results section.
  5. Clear & Try Again: Use the Clear All button to reset and solve new problems.

For best results, double-check your inputs. The calculator will alert you if the values do not form a valid triangle. Use the tool on any device for quick, accurate triangle calculations.